Verb Forms (الأوزان العشرة) — Morphological Rules

Arabic triliteral verbs appear in ten primary derived patterns. ACE detects forms automatically using consonant patterns, vowels, and prefixes (e.g., ta-, sta-, in-).

Form I — الفعل الثلاثي المجرد

• Pattern: فَعَلَ / فَعِلَ / فَعُلَ
• Imperfect: يَفْعَلُ / يَفْعِلُ / يَفْعُلُ

• كَتَبَ → يَكْتُبُ

Form II — التفعيل (faʕʕala)

• Pattern: فعّل
• Doubling of the second radical

• دَرَّسَ → يُدَرِّسُ

Form III — المفاعلة (fāʕala)

• Pattern: فاعَلَ
• Imperfect: يُفاعِلُ

Form IV — الإفعال (afʕala)

• Prefix: أَ- / أُ-
• Imperfect: يُفْعِلُ

Form V — التفعُّل (tafaʕʕala)

Derived from Form II with prefix تَـ.

Form VI — التفاعُل (tafāʕala)

Derived from Form III with prefix تَـ.

Form VII — الإنفعال (infaʕala)

• Prefix: اِنْـ
• No passive forms

Form VIII — الإفتعال (iftaʕala)

• Prefix: اِتَّـ / اِطَّـ (assimilation rules apply)

Form IX — الإفعال للألوان (ifʕalla)

Rare; used for colors and defects.

Form X — الإستفعال (istafʕala)

• Prefix: اِسْتَـ
• Imperfect: يَسْتَفْعِلُ

ACE detects forms using:
1) prefix patterns
2) gemination (shaddah)
3) vowel templates
4) assimilation rules (for Form VIII)